When I used this method a few years ago, with Ada from the Ubuntu repository, it worked fine. Now, with my installation from Adacore, not so anymore.

The method consists of 2 commands (time.h as example)

1. g++ -c -fdump-ada-spec -C /usr/include/time.h
2. gcc -c -gnat05 *.ads

While the first command executes without any problem, the second one returns:

gcc: fatal error: cannot execute ‘gnat1’: execvp: No such file or directory

It doesn't depend on the -gnat05 option. There is indeed no gnat1 in the bin directory of the Ada installation. Mine is version 2021. I am reluctant to install the GNU version in parallel, I might mix up things.

Any other idea?